Algae

Members of a group of mostly aquatic, photosynthetic organisms, algae provide much of Earth's oxygen, serve as the food base for almost all aquatic life, and provide foods and industrial products, including petroleum products.

Algae can be used to reduce pollution (greenhouse gases). Scientists and experts have been working to use algae to transform the world's energy needs and slow climate change. (Source: Britannica Online Encyclopedia, USA Today / Photo: Flickr)